This invention relates to tape, in particular, tape reinforced by means of filaments.
One embodiment of a fiber optic cable comprises, in part, one to 24 (or more) optical fibers, each of which is usually contained in a loose tube made of polymeric material for protection. Because optical fibers are often used in environments that are subject to high levels of moisture, hydrophobic gels are generally applied to the surface of the optical fiber-containing tubes. These gels are typically applied just prior to the time a protective jacket is extruded over the bundle of optical fibers. The basic element of this technology, the optical fiber, is a small, transparent filament that guides optical energy in the form of visible light or infrared radiation. This filament consists of an inner transparent silica (glass) core and outer transparent material, commonly referred to as the cladding. Light is guided in the core by reflections at the core-cladding interface. These reflections occur because of a difference in the refractive index between the higher index core and lower index cladding. Reflections of this type, between high and low index media, require that the interface be smooth, so that attenuation of the optical signal, i.e. decrease in signal transmission, is minimized.
The individual optical fibers of the fiber optic cable are generally bound by tapes or yarns. Yarns currently used in binding bundles of optical fibers frequently attenuate the optical signal by placing high stress at various points on individual optical fibers. In particular, attenuation of the signal occurs because localized pressure at the point where the yarn contacts the loose optical fiber-containing tube causes the tube to contact the optical fiber, which further causes microbending of the optical fiber. This microbending phenomenon further causes an altering of the reflection pattern in the fiber. While tapes used to bind optical fibers do not adversely affect the strength of the optical signal, they are not sufficiently strong to withstand the environment in which the cables are used. Because of this inherent lack of strength of binding tapes, most tapes are wrapped around bundles of optical fibers so as to have the edges of the tape overlap. Although this overlapping tends to compensate for the weakness of the tape, it gives rise to an additional problem, i.e. because of the overlapping of the tape, the aforementioned hydrophobic gel cannot be applied directly to the surface of the optical fiber-containing tubes, resulting in a higher probability of moisture damage to the optical fibers.
It would be desirable to develop tapes for binding optical fibers that could both replace the yarns that cause the high localized stress on the optical fibers and be sufficiently strong to withstand the environment in which optical fibers are used.